Warm the pipes up to where you can just touch them before having to pull your hand away. Then scrub Gently! with white 3m scrubbies pads with a solution of water and simple green. rinse and dry off residue. This may take two or more times. After a bit of time the stain will eventually disappear. Coated sidepipes are pretty resistant to most plastics that melt on them.
Like Masnaka said " like a self-cleaning oven".
Don't feel too bad you are in good company many of us have done the same bone-headed thing or worse to our sidepipes
